Observation of a gravitational Aharonov-Bohm effect

Gravitational interference The Aharonov-Bohm effect is a quantum mechanical effect in which a magnetic field affects the phase of an electron wave as it propagates along a wire. Atom interferometry exploits the wave characteristic of atoms to measure tiny differences in phase as they take different paths through the arms of an interferometer. Overstreet et al . split a cloud of cold rubidium atoms into two atomic wave packets about 25 centimeters apart and subjected one of the wave packets to gravitational interaction with a large mass (see the Perspective by Roura). The authors state that the observed phase shift is consistent with a gravitational Aharonov-Bohm effect. —ISO

Analysis of a Casimir-driven parametric amplifier with resilience to Casimir pull-in for MEMS single-point magnetic gradiometry

The Casimir force, a quantum mechanical effect, has been observed in several microelectromechanical system (MEMS) platforms. Due to its extreme sensitivity to the separation of two objects, the Casimir force has been proposed as an excellent avenue for quantum metrology. Practical application, however, is challenging due to attractive forces leading to stiction and device failure, called Casimir pull-in. In this work, we design and simulate a Casimir-driven metrology platform, where a time-delay-based parametric amplification technique is developed to achieve a steady-state and avoid pull-in. We apply the design to the detection of weak, low-frequency, gradient magnetic fields similar to those emanating from ionic currents in the heart and brain. Simulation parameters are selected from recent experimental platforms developed for Casimir metrology and magnetic gradiometry, both on MEMS platforms. While a MEMS offers many advantages to such an application, the detected signal must typically be at the resonant frequency of the device, with diminished sensitivity in the low frequency regime of biomagnetic fields. Using a Casimir-driven parametric amplifier, we report a 10,000-fold improvement in the best-case resolution of MEMS single-point gradiometers, with a maximum sensitivity of 6 Hz/(pT/cm) at 1 Hz. Further development of the proposed design has the potential to revolutionize metrology and may specifically enable the unshielded monitoring of biomagnetic fields in ambient conditions.

Gravity induced quantum interference on gravitational wave background

Gravity-induced quantum interference is an experiment that exhibits how a gravitational effect appears in quantum mechanics.1 In this famous experiment, gravity was added to the system just classically. In our study, we will do the related calculations on a gravitational wave background. We will argue that the effect of gravitational wave would be detectable in this quantum mechanical effect.

Modeling of 2DEG characteristics of InxAl1−xN/AlN/GaN-Based HEMT Considering Polarization and Quantum Mechanical Effect

A comprehensive model for 2DEG characteristics of InxAl1−xN/AlN/GaN heterostructure has been presented, taking both polarization and bulk ionized charge into account. Investigations on the 2DEG density and electron distribution across the heterostructure have been carried out using solutions of coupled 1-D Schrödinger-Poisson equations solved by an improved iterative scheme. The proposed model extends a previous approach allowing for estimating the quantum mechanical effect for a generic InAlN/GaN-based HEMT within the range of the Hartree approximation. A critical AlN thickness (~2.28 nm) is predicted when considering the 2DEG density in dependence on a lattice matched In0.17Al0.83N thickness. The obtained results present in this work provide a guideline for the experimental observation of the subband structure of InAlN/GaN heterostructure and may be used as a design tool for the optimization of that epilayer structure.

Analysis and modeling of quantum capacitance on graphene single electron transistor

Graphene single electron transistor (SET) as a coulomb blockade (CB) device operates based on the quantum mechanical effect. Its desired current is achieved by overcoming the CB energy that depends on the total capacitance of SET. Therefore, small size of graphene quantum capacitance is suitable for SET structure because it plays a dominant role in the total capacitance. In this paper, the density of state (DOS) model of graphene SET is suggested because of its important effect on many physical properties. Furthermore, carrier concentration as a key factor in quantum capacitance is modeled. Finally, the quantum capacitance of graphene SET based on the fundamental parameters is modeled and compared to the experimental data, so an acceptable agreement between them is reported. As a result, silicon SET can be replaced with graphene SET because of its lower quantum capacitance and also higher operation speed than the silicon one.

How cold atoms got hot: an interview with William Phillips

William Phillips of the National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland, shared the 1997 Nobel Prize in physics for his work in developing laser methods for cooling and trapping atoms. Interactions between the light field and the atoms create what is dubbed an ‘optical molasses’ that slows the atoms down, thereby reducing their temperature to within a fraction of a degree of absolute zero. These techniques allow atoms to be studied with great precision, for example measuring their resonant frequencies for light absorption very accurately, so that these frequencies may supply very stable timing standards for atomic clocks. Besides applications in metrology, such cooling methods can also be used to study new fundamental physics. The 1997 Nobel award was widely considered to be a response to the first observation in 1995 of pure Bose–Einstein condensation (BEC), in which a collection of bosonic atoms all occupy a single quantum state. This quantum-mechanical effect only becomes possible at very low temperatures, and the team that achieved it, working at JILA operated jointly by the University of Colorado and NIST, used the techniques devised by Phillips and others. Since then, cold-atom physics has branched in many directions, among them being attempts to make a quantum computer (which would use logic operations based on quantum rules) from ultracold trapped atoms and ions. ‘National Science Review’ spoke with Phillips about the development and future potential of the field.